Chemokines are chemotactic proteins that have the potential to attract macrophages, T-cells, eosinophils, basophils, neutrophils and endothelial cells to sites of inflammation and tumor growth. Chemokines are typically low molecular mass (7-9 kD) proteins that can be divided into four subfamilies: CC (or β-chemokines), CXC, C (or γ-chemokines) and CX3C (or δ-chemokines). The chemokines are categorized through their primary amino acid structure. The CXC subfamily is characterized by two conserved Cys residues (C) near the N-terminus and separated by an amino acid (X). The CXC-chemokines include, for example, interleukin-8 (IL-8), neutrophil-activating protein-1 (NAP-1), neutrophil-activating protein-2 (NAP-2), GROα, GROβ, GROγ, ENA-78, GCP-2, IP-10, MIG and PF4. The CXC subfamily of chemokines is further characterized by the presence or absence of a specific amino acid sequence, glutamic acid-leucine-arginine (or ELR for short) immediately before the first Cys residue of the CXC motif. Those chemokines with the ELR motif (ELRCXC) are important for the recruitment and activation of neutrophils to sites of inflammation. For example, GROα and IL-8 are ELRCXC chemokines.
The CXC-chemokines mediate their chemotactic activity through interaction with the chemokine receptors CXCR1 and CXCR2. CXCR1 binds IL-8 and GCP-2 with high affinity while CXCR2 binds all ELRCXC chemokines with high affinity.
Since CXC-chemokines promote the accumulation and activation of neutrophils, CXC-chemokines have been implicated in a wide range of acute and chronic inflammatory disorders including COPD, psoriasis and rheumatoid arthritis. (Baggiolini et al., FEBS Lett. 307:97,1992; Miller et al., Crit. Rev. Immunol. 12:17, 1992; Oppenheim et al., Annu. Rev. Immunol. 9:617, 1991; Seitz et al., J. Clin. Invest. 87:463, 1991; Miller et al., Am. Rev. Respir. Dis. 146:427, 1992; and Donnely et al., Lancet 341:643, 1998).
ELRCXC chemokines, including IL-8, GROα, GROβ, GROγ, NAP-2, and ENA-78 (Strieter et al. J. Biol. Chem. 270:27348-57, 1995), have also been implicated in the induction of tumor angiogenesis (new blood vessel growth). Angiogenic activity is due to ELRCXC-chemokine binding to, and activation of CXCR2, and possibly CXCR1 for IL-8, expressed on the surface of vascular endothelial cells (ECs) in surrounding vessels.
Many different types of tumors have been shown to produce ELRCXC chemokines. Chemokine production has been correlated with a more aggressive phenotype (Inoue et al. Clin. Cancer Res. 6:2104-2119, 2000) and poor prognosis (Yoneda et al. J. Nat. Cancer Inst. 90:447-454, 1998). Chemokines are potent chemotactic factors and the ELRCXC chemokines, in particular, have been shown to induce EC chemotaxis. Thus, these chemokines are thought to induce chemotaxis of endothelial cells toward their site of production in the tumor. This may be a critical step in the induction of angiogenesis by the tumor. Inhibitors of CXCR2 or dual inhibitors of CXCR2 and CXCR1 will inhibit the angiogenic activity of the ELRCXC chemokines and therefore block the growth of the tumor. This anti-tumor activity has been demonstrated for antibodies to IL-8 (Arenberg et al. J. Clin. Invest. 97:2792-2802, 1996), ENA-78 (Arenberg et al., J. Clin. Invest. 102:465-72, 1998), and GROα (Haghnegandar et al., J. Leukoc. Biology 67:53-62, 2000).
Therefore, there is a need in the art to find CXCR2 inhibitor compounds and modulator compounds that can be used as pharmaceutical compounds. There remains a need for compounds that are capable of modulating activity at CXC-chemokine receptors. For example, conditions associated with an increase in IL-8 production (which is responsible for chemotaxis of neutrophil and T-cell subsets into the inflammatory site and growth of tumors) would benefit by compounds that are inhibitors of IL-8 receptor binding. The present disclosure was made to satisfy this need.